Field of the Invention
Aspects of the present invention generally relate to control of a manual feed tray in an image forming apparatus.
Description of the Related Art
Image forming apparatuses of the electrophotographic type configured to feed sheets placed on a sheet feed cassette or a manual feed tray to perform image formation. Nowadays various types of sheets are available in the marketplace. Under such circumstances, a manual feed tray is used to feed, for example, sheets of grammages that do not comply with sheet feed cassettes, sheets of coated paper having a slippery surface property, and long sheets greater in length than currently available sheets. Japanese Patent Application Laid-Open No. 11-189344 discusses an image forming apparatus having a mode for causing a bottom plate to lower to such a position as to disable feeding of sheets each time image formation is completed and a mode for causing the bottom plate to be held in such a position as to enable feeding of sheets even after image formation is completed. In such an image forming apparatus, selecting any one of the modes is allowed. In the case of such a manual sheet feed device, when runout of sheets in the manual sheet feed device during image formation is detected, the bottom plate is caused to lower so as to enable replenishment of sheets, so that user operability is improved. Moreover, for example, since the bottom plate is caused to lift at the timing when sheets are set on the manual feed tray, a time required to output the first sheet is shortened, so that user operability is further improved.
However, conventional configurations have the following issues. In the above-mentioned image forming apparatus, the bottom plate lifts even when any type of sheet, such as a sheet with special ink coated thereon, for example, carbon paper or non-carbon paper, is set on the manual feed tray. Therefore, lifting of the bottom plate brings a sheet feed roller and the sheet into contact with each other, and such a contact state is maintained. This may lengthen the time for which the sheet feed roller and the sheet are in contact with each beyond necessity. In this case, for example, ink attached to the sheet, paper powder, or loading material of paper may adhere to the sheet feed roller. If, for example, ink, paper powder, or loading material of paper adheres to the sheet feed roller, soiling of the sheet feed roller may cause soiling of sheet subsequently conveyed or a conveyance failure, such as slippage of the sheet feed roller.